1. Department of Chemistry and Institute for Advanced Research, Nagoya University, Nagoya, 464-8602, Japan
2. Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-2320, United States
3. School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
4. Stanford Institute for Materials and Energy Science, Stanford University, Stanford, California 94305, United States